IEEE PAR1789 Compliant Low-Cost Permanent Emergency Lamp Based on a Series Quasi-Resonant Converter in Combination With a Low-Dropout Current Regulator

Permanent emergency LED lamps ensure continuous illumination and serve as backup lighting during power outages. Key design considerations include maximizing efficiency and minimizing component count. Dimming techniques, such as Pulse Width Modulation (PWM), are commonly used to regulate light output without chromaticity shifts. However, the IEEE PAR1789 standard advises using PWM frequencies above 1.25 kHz to mitigate flicker and its adverse health effects, which complicates driver design. This paper introduces a cost-effective solution for permanent emergency LED lamps based on a quasi-resonant buck (QRB) converter in series with a low-dropout current source (LDOCS). The QRB minimizes power losses in the LDOCS, while the LDOCS regulates both the lamp and battery currents using a 2 kHz PWM reference, thereby effectively reducing flicker-related risks. Additionally, the integration of the QRB and LDOCS mitigates the audible noise caused by magnetostriction by attenuating the 2 kHz current component in the circuit's inductance. The proposed driver employs economical components, including an L6562A control integrated circuit, general-purpose operational amplifiers, and a basic microcontroller. An experimental prototype validates the effectiveness of the proposed approach.